Dr. Tucker:          Welcome to the Arthroscopy Association's Arthroscopy Journal Podcast. The views expressed in this podcast do not necessarily represent the views of the Arthroscopy Association or the Arthroscopy Journal. I'm Dr. Chris Tucker from the Walter Reed National Military Medical Center and founder of the podcast. 

Dr. Tucker:          I'd like to introduce Dr. Andrew Sheean from San Antonio, Texas. Dr. Sheean is an assistant professor in the Department of Orthopedic Surgery at the San Antonio Military Medical Center and a familiar voice to our listeners as one of our podcast hosts. Today, however, I have the privilege of putting Andy in the hot seat as he serves as our guest author. Dr. Sheean was the lead author on a recent systematic review titled "Does an Increased Critical Shoulder Angle Affect Re-tear Rates and Clinical Outcomes Following Primary Rotator Cuff Repair? A Systematic Review", which was published in the October 2019 issue of the Arthroscopy Journal. His coauthors included Dr. Darren De SA, Taylor Woolnough, Daniel Cognetti, Jeffrey Kay, and Stephen Burkhart. 

Dr. Tucker:          Welcome Andy, and thanks for joining me. 

Dr. Sheean:        Thanks Chris. This is exciting, and I'm glad to be talking to you tonight. 

Dr. Tucker:          Andy, can you start us off with some brief background on this review and where the idea came from to study this topic? 

Dr. Sheean:        Yeah, absolutely. I'd be remiss if I didn't first give a shout out to to my coauthors, particularly Darren De SA, who was a co-fellow of mine at the University of Pittsburgh, who's currently at McMaster University doing really exciting things. He and his team have been prolific in terms of what it is they've been able to accomplish in terms of churning out a lot of these systematic reviews that are helping us wrap our minds, or wrap our hands around I should say, some really important clinical questions. And obviously, Dr. Burkhart's contribution as well, he's written a couple of papers about rotator cuff repair and so we were excited to have his input on this as well. And then I was excited to get one of our residents here in San Antonio, Dan Cognetti, involved in this project. 

Dr. Sheean:        So the topic itself is interesting to me. Rotator cuff healing, or a lack thereof in certain circumstances, is a vexing problem, as you well know. And so, Darren and I started kicking this around while we were actually fellows, and thinking about different things that hadn't already been looked at in terms of optimizing rotator cuff repair outcomes. More and more continues to be written about biologic factors, constructs, double row/single row, but there is also an increasing body of literature to suggest that there are certain acromion morphologies that may predispose rotator cuff repairs to higher rates of re-tear. And so that was what really got our wheels spinning and interested in investigating this a little bit further. 

Dr. Tucker:          Yeah. I think it's an exciting topic as well, I really enjoyed reading some of these really well done systematic reviews. So jumping into the specifics on this one, the stated purpose of y'alls study was to determine if an increased critical shoulder angle predisposed patients to higher re-tear rates and worse clinical outcomes after cuff repair. Can you first explain for us what defines the critical shoulder angle, and why this could potentially have an effect on rotator cuff repair surgery? 

Dr. Sheean:        Yes. So the critical shoulder angle actually combined the chromium index and glenoid inclination, and so for those guys and gals that are on a treadmill or on their way home from work, what the critical shoulder angle is is the angle that is measured between two lines. The first line is a line drawn tangent to the glenoid from the superior to inferior direction, and then the second line is a line drawn from the inferior most aspect of the glenoid, the lateral most projection of the acromion. So that's how you measure it, and hopefully people can picture that if they're listening. 

Dr. Sheean:        From a biomechanical standpoint, it's been suggested or hypothesized that a more laterally overhanging acromion creates a increased vertical deltoid vector, which would increase sheer forces across the glenohumeral joint, across the humeral head, and then lead to decreased compressive forces within the glenoid, all of which would put increased strain on a rotator cuff repair. 

Dr. Tucker:          I think it's a super interesting concept. I think, as I gleaned from your paper, it sounds like since both the acromion index and the glenoid inclinations have both previously been associated with rotator cuff tears, combining the two into a new, seemingly more simply measured a single angle, could potentially be a prognostic factor for surgeons who are handling these kinds of cases. So can you tell us now how you went about investigating your stated purpose, of determining this relationship between that critical shoulder angle and the rotator cuff repair re-tear rates and outcomes? 

Dr. Sheean:        Yep. And I think we can get into this a little bit more when we start talking about the nuances and specifics of doing these types of studies. But when you do a systematic review, I think one of the purposes always is trying to get a sense of what has been written about it, or a particular topic I should say, and what are the shortcomings in the literature. Such that you can know the extent of it, but also too you can start asking different questions or coming up with different types of studies, and may be able to fill in some of these knowledge gaps. 

Dr. Sheean:        And so it's important that when you set out to do something like this, to ask yourself one discreet question, and again, our question is to determine what has been written about the relationship, or lack thereof, between an critical shoulder angle and rotator cuff re-tear rate. 

Dr. Tucker:          So let's take a quick sidebar away from the topic itself and just talk about systematic reviews, since you mentioned it. Can you just briefly explain for us the process for writing this type of review article, and maybe what makes it different from other review articles, such as a meta analysis, and perhaps touch on the methods to conduct this type of review? For example, what are the PRISMA guidelines and how does that pertain to a systematic review? 

Dr. Sheean:        Sure. The distinction between a systematic review and a meta analysis is really, really important, and the way that I think about it is in terms of a systematic review being a qualitative summary. You arrive at your conclusion, or all of your data is based upon a list of papers that are obtained in a systematic fashion, but there really isn't a whole lot of data analysis or crunching of the numbers between studies. There are some circumstances, and we did it there, where if you're able to identify papers with similar methodology that you can then make some sub-analyses and use some nuance statistics to make some generalizations. 

Dr. Sheean:        Whereas a systematic review is a qualitative summary of the literature, a meta analysis is a quantitative type study. You're actually taking results from similar studies, in terms of their methodologies and their results, and combining them in order to make overarching statements or conclusions about the body of literature and about those data. 

Dr. Sheean:        And I should also say that, for those of our listeners who haven't done so, I would really recommend that they go back and read the article that Drs. Harris, Rossi, Cote and Dhawan published in Arthroscopy Journal in 2017 talking about all of these things really elegantly in terms of the perils and pitfalls of systematic reviews and meta analyses and data pooling, and so on and so forth. And it's really important when you set out to do a systematic review, and I mentioned this earlier, but is to ask one discreet question, and if you can distill everything down to a yes or no question, you're really setting yourself up in order to, I think, perform one of these studies in a way that that helps the readers understand what's been written in what has been written about a particular topic. 

Dr. Sheean:        With respect to the PRISMA guidelines, that's an acronym that stands for Preferred Reporting Items for Systematic Reviews and Meta-Analyses, and this is a checklist, it's a 27-item checklist, pretty much lays out exactly how studies like this should be done and should be reported. It was first described in 2009, since been refined somewhat. But the idea behind it is that you follow this set of guidelines, and another independent author or group of authors should be able to perform the exact same study using those methods and hopefully arrive at the same conclusion. So it's about creating a quality product and using systematic quality methods in order to generate conclusions. 

Dr. Tucker:          Thanks, I think that was a great summary. I appreciate the thoroughness and explanation, especially for those of us who may not have written one of these before or aren't particularly as involved in the data crunching research. And I think it helps clarify what exactly we should take away from this type of article. 

Dr. Sheean:        I should mention that as it pertains to actually the nuts and bolts of doing the review, that's where having Darren De SA and his team up at McMaster, these guys very much have this system down in terms of being able to generate a search quickly using a search engine, which then yields a big list of titles. And then being able to distill that down quickly into, in our case, six studies, that's important. And so if you could have those, again, nuts and bolts figured out beforehand, it really streamlines things and it allows you to, from the time that you say "go" in terms of starting answering your question until the time that you have generated your list of articles, ideally you'd want that to be a relatively short amount of time so that ultimately the product that you're generating is something that is a up-to-date, accurate snapshot of what has been written about something. 

Dr. Tucker:          All right. So what can you tell us about the key findings for this specific systematic review? 

Dr. Sheean:        Sure. So broadly speaking, I was actually pretty surprised to see that there were really only six papers that we were able to identify that met our inclusion criteria. There was one Level 1 study, four Level 4 studies, and one Level 5 study. Overall, these six studies were comprised of 473 patients, there were three comparative studies, and all three of the comparative studies did demonstrate that an increased re-tear rate after rotator cuff repair was associated with an increased critical shoulder angle. 

Dr. Sheean:        The mean critical shoulder angle in those three studies that were associated with re-tear ranged from 37 to 40 degrees, while the mean range of critical shoulder angles that were not associated with repair re-tear was 34 to 37 degrees. Interestingly, only one study, the paper by Dr. Christian Gerber's group, specifically sought to assess the effect of a corrective acromioplasty, that is to say they looked at their critical shoulder angle pre and post operatively. 

Dr. Tucker:          So it's interesting to me that there are so few studies, and I guess one of my off-the-cuff questions for you is, after reading all these and really delving into the nuances of this studies, do you think it's more of a correlation or an association between the critical shoulder angle and the re-tearing of a cuff repair? 

Dr. Sheean:        That's a great question. I think that this is a really, really, really tough nut to crack because there are so many things that go into rotator cuff re-tear. The size of the tear initially, the repair type, patient co-morbidities. Were they diabetics? Did they smoke? And, I'm going to use a word that I think is becoming increasingly popular, there just wasn't the granularity amongst these six studies, I think, to make any substantive statements about correlation versus association. So I'm inclined at this point, I guess, to cop out and maybe say it's tough to say based upon what little has been written on it about it. 

Dr. Tucker:          Yeah. I don't think that's a cop out, I think that's probably just a very honest answer from somebody who's looked at all the literature closer than most of us. And has maybe one of the key findings from the systematic review is just that there's insufficient evidence out there to currently answer some of these questions, and that's probably a fair conclusion. So overall, were any of the findings from your study surprising to you folks at all? 

Dr. Sheean:        Not really. Based upon, again, some of the biomechanics of why people think that the critical shoulder angle may play a role in terms of, again, increasing the sheer forces across the repair site, that stands to reason that that would put a particular repair in a position of vulnerability. I think that what is definitely needed from this, from our analysis, one of the points I'd like the readers to take home, is that more needs to be studied on this. Not just on, "Does a critical shoulder angle lead to a increased re-tear rate?" but how can we modulate this? 

Dr. Sheean:        Peter Millett wrote a really nice paper, that was also published in Arthroscopy Journal within the last, I think, two or three years, it was a cadaveric study. But they went back and they did an acromioplasty, and then took fluoroscopic images before and after and were able to quantify the extent to which the critical shoulder angle can be modified within acromioplasty. And so I think that's the next frontier for those people that are really interested in examining this, and describing it in more detail is if this really matters, is being able to say that, "We did an acromioplasty, here was our critical shoulder angle preoperatively, here was postoperatively," and then shake out your affects and your outcomes based upon that. 

Dr. Sheean:        And as I mentioned, Dr. Gerber's group did do that, but we need more than just one study, we need larger studies, things like that. And more standardization across patients in terms of, again, controlling for some of the things that are really pretty significant confounders, patient-related factors, diabetics, smoking, things like that. 

Dr. Tucker:          The limited number and the heterogeneity of currently available literature obviously is what's limiting the strength of the observations that we're seeing. The surgical techniques vary, the modalities of post-op rotator cuff healing evaluation are deferring. The majority of the studies on this topic don't even report on postoperative critical shoulder angles, making it pretty much impossible to conclude whether this procedure is having an effect on patient outcomes. Why do you think this is? Do you think it's just too new of a concept, are we just getting into it? And do you think we can achieve, as a profession, answering this question? 

Dr. Sheean:        Yeah. Well, as it pertains to the relatively few number of studies, really the critical shoulder angle, I think was described in 2013, and so we're not even 10 years into it. And I think when you go back and you look at the six papers that we included in our final analysis, they were all published between 2017 and 2018, so I think that this just represents an idea that's very much in its infancy. And so, I think the big takeaway of this paper is not necessarily that, "Well, you should be doing a larger acromioplasty to change your critical shoulder angle because three of the comparative studies showed that critical shoulder angles greater than 37 degrees resulted in re-tear rates," I think that the main takeaway from this paper should be, "There's only been six studies published on this," and I think that this warrants folks in the future looking long and hard about trying to add to what's been written in this and help us try to answer this question. 

Dr. Sheean:        Do I think it's an answerable question? I think, again, it's somewhat of a daunting proposition, but I think it is possible with an adequately powered study. And with, I think, again, the standardization of it's surgical technique, and incorporating postoperative radiographs in order to, again, assess the extent to which that critical shoulder ankle is changed. I think that there could be some meaningful contribution to the body of literature as it pertains to this particular variable. 

Dr. Tucker:          Yeah, I agree with you. I think anything is potentially answerable, but like you said, it's just going to require an appropriately powered study and well-defined parameters which, like most research, takes time, money and energy. 

Dr. Tucker:          So what's your current practice, with respect to evaluating patients with rotator cuff disease as it relates to the critical shoulder angle? Are you actively measuring it in all your patients preoperatively? And if so, how is this playing into your decision making process? Whether that be earlier recommendations for surgery, if it's a higher angle. Or is it affecting your technique of doing your cuff repairs, or even your postop rehab program? And are you doing any of these lateral acromioplasty's yourself? 

Dr. Sheean:        So I'd say I definitely pay more attention to it now than I did 6 to 12 months ago, before we finalize everything with this. I do not routinely measure it on every patient that I see in my clinic with a rotator cuff tear. However, for the patients that I think are going to be difficult in terms of getting their repair to heal, or if there's a terror that I think is going to be a particular bad actor, a large tear that's chronic in the setting of a smoker, a diabetic, someone that's older, someone that's got all of these things stacked against them to begin with in terms of whether or not I'm going to be able to achieve a durable repair, then then adding this to the milieu. 

Dr. Sheean:        Or I should say that the things that I'm going to be doing inter-operatively, whether that be releases, adding biologics, using link double repairs, all things that I believe are really important to maximizing likelihood of healing and optimizing clinical outcomes, then I think that adding a lateral-based acromioplasty to decrease a potentially increased critical shoulder angle, and it is a reasonable adjunct, provided that you don't go crazy as has been described in terms of preserving that deltoid fascia. 

Dr. Sheean:        But I guess the short answer to your question is, no, I don't measure it in everybody. But the people that I'm worried about, I am paying attention to it and I'm considering trying to decrease that parameter postoperatively. 

Dr. Tucker:          Yeah, I think that's fair. As far as one of my mentors told me, you never want to be the first, and you certainly don't want to be the last, to adopt a new technique or a new approach to anything. So I think this is an evolving concept and it's new, and I think it potentially has its place in practice, and that's what we're all trying to figure out with studies like yours so appreciate your contribution to that effort. 

Dr. Tucker:          So to close, can you just share with our listeners, you're one or two take home points with respect to the critical shoulder angle and rotator cuff repair outcomes that they can potentially incorporate into their own clinical practices? 

Dr. Sheean:        Sure. So if we thought that we knew all of the factors that affected rotator cuff repair, clinical outcomes, we didn't. We can add this one to that rapidly expanding list. I think that it's important that the listeners understand that the critical shoulder angle is, again, very much in its infancy, and based upon the results of the review it's pretty clear that hasn't been a lot written about it, so I think this is an area that is certainly ripe for further investigation. 

Dr. Sheean:        And then lastly, like I mentioned earlier, for those patients that are a particular risk for re-tear, older folks, big tears, diabetics, smokers, strongly consider assessing the critical shoulder angle in your preoperative evaluation, and thinking to yourself, "What can you do in order to maximize the likelihood of that repair healing, and minimize the stresses and strains that are put on that repair by something like a lateral overhanging acromion?" 

Dr. Tucker:          Great. I think that's awesome, Andy. Thanks again for sharing your thoughts with us. Dr. Sheean's article titled "Does an Increased Critical Shoulder Angle Affect Re-tear Rates and Clinical Outcomes Following Primary Rotator Cuff Repair? A Systematic Review", can be found in the October 2019 issue of the Arthroscopy Journal, which is available online at www.arthroscopyjournal.org. 

Dr. Tucker:          Andy, thanks again for joining me. 

Dr. Sheean:        Thanks for having me, Chris. 

Dr. Tucker:          This concludes this edition of the Arthroscopy Journal podcast. Thank you for listening, please join us again next time.